Stability of Y2O3:Tm,Yb phosphor thin films during cathodoluminescence and upconversion

An Y2O3:Tm,Yb thin film was synthesized by the sol-gel method using spin coating. X-ray powder diffraction revealed the formation of a Y2O3 cubic phase. The cathodoluminescence and upconversion photoluminescence of the film were investigated, including assessment of emission stability. Auger electron spectroscopy was used to monitor its chemical state concurrently with the cathodoluminescence intensity using the same electron beam. Auger peaks associated with carbon, yttrium and oxygen were detected and their Auger peak-to-peak heights indicated that carbon was removed from the surface during the initial stage of degradation, whereas yttrium and oxygen remained almost unchanged. The cathodoluminescence degradation of the Tm emissions at 457 nm and 975 nm exhibited a continuous decline until the electron dose was about 100 C/cm2 and then stabilized. The upconversion photoluminescence intensity of the Tm emission at 488 nm remained stable for a period of 28 h and did not exhibit degradation.